1. Field of the Invention
The present invention relates to a fluid-filled vibration damping device used for an automotive engine mount and the like, for example, and particularly relates to technology that can provide effective and simple resolution measures for noise due to cavitation that occurs with input of an impact load and the like.
2. Description of the Related Art
From the past as one type of vibration damping device such as a vibration damping coupling unit or vibration damping support unit interposed between members constituting a vibration transmission system, a fluid-filled vibration damping device that uses a vibration damping effect based on the fluid flow action of fluid sealed in the interior is known. This fluid-filled vibration damping device, for example as noted in Japanese Unexamined Patent Publication No. JP-A-2005-337348, has a structure that includes a primary liquid chamber which gives rise to pressure fluctuations based on deformation of the main rubber elastic body when vibration is input, and an auxiliary liquid chamber which gives rise to pressure fluctuations relative to the primary liquid chamber when vibration is input, and these are in communication by an orifice passage. Also, a vibration damping effect is made to be exhibited based on the fluid flow action of non-compressible sealed fluid made to flow through the orifice passage between the primary liquid chamber and the auxiliary liquid chamber which give rise to relative pressure fluctuations when vibration is input.
However, with this kind of fluid-filled vibration damping device, there are cases when noise or vibration generated during input of an impact load becomes a problem. That noise or the like is thought to be due to cavitation air bubbles generated by a rapid decrease in pressure of the primary liquid chamber by input of an impact load.
For this kind of problem, as noted in U.S. Pat. No. 7,306,210, proposed is also a constitution for which a shunt flow path is provided that is equipped with a relief valve or the like between a pressure receiving chamber correlating to the primary liquid chamber and an equilibrium chamber correlating to the auxiliary liquid chamber, and for which excessive negative pressure in the primary liquid chamber is rapidly eliminated.
However, a relief valve, shunt flow path or the like need to be specially formed, and there was the problem that an increase in the number of parts and the structure becoming complex were unavoidable.